Abnormalities of the enzyme, lipoamide dehydrogenase (LAD), have been described in some families with the recessive neurological syndrome, Friedrich's ataxia. As part of the study of this association, LAD from tissues of humans without ataxia will be partially purified by a novel method and the relative molecular weight, isoelectric point, kinetic constants and other characteristics of the LAD determined. In the future, properties of LAD from ataxic patients will be compared with non-ataxic controls. The same methods will be used to investigate whether or not three are tissue-specific isoenzymes of LAD in laboratory animals and, in the future, in human cadaver tissues.